//
// Copyright (c) 2016-2017 Vinnie Falco (vinnie dot falco at gmail dot com)
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
// Official repository: https://github.com/boostorg/beast
//

#ifndef BOOST_BEAST_DETAIL_SHA1_HPP
#define BOOST_BEAST_DETAIL_SHA1_HPP

#include <algorithm>
#include <cstdint>
#include <cstring>

// Based on https://github.com/vog/sha1
/*
    Original authors:
        Steve Reid (Original C Code)
        Bruce Guenter (Small changes to fit into bglibs)
        Volker Grabsch (Translation to simpler C++ Code)
        Eugene Hopkinson (Safety improvements)
        Vincent Falco (beast adaptation)
*/

namespace moon {

namespace sha1 {

    static std::size_t constexpr BLOCK_INTS = 16;
    static std::size_t constexpr BLOCK_BYTES = 64;
    static std::size_t constexpr DIGEST_BYTES = 20;

    inline std::uint32_t rol(std::uint32_t value, std::size_t bits) {
        return (value << bits) | (value >> (32 - bits));
    }

    inline std::uint32_t blk(std::uint32_t block[BLOCK_INTS], std::size_t i) {
        return rol(block[(i + 13) & 15] ^ block[(i + 8) & 15] ^ block[(i + 2) & 15] ^ block[i], 1);
    }

    inline void
    R0(std::uint32_t block[BLOCK_INTS],
       std::uint32_t v,
       std::uint32_t& w,
       std::uint32_t x,
       std::uint32_t y,
       std::uint32_t& z,
       std::size_t i) {
        z += ((w & (x ^ y)) ^ y) + block[i] + 0x5a827999 + rol(v, 5);
        w = rol(w, 30);
    }

    inline void
    R1(std::uint32_t block[BLOCK_INTS],
       std::uint32_t v,
       std::uint32_t& w,
       std::uint32_t x,
       std::uint32_t y,
       std::uint32_t& z,
       std::size_t i) {
        block[i] = blk(block, i);
        z += ((w & (x ^ y)) ^ y) + block[i] + 0x5a827999 + rol(v, 5);
        w = rol(w, 30);
    }

    inline void
    R2(std::uint32_t block[BLOCK_INTS],
       std::uint32_t v,
       std::uint32_t& w,
       std::uint32_t x,
       std::uint32_t y,
       std::uint32_t& z,
       std::size_t i) {
        block[i] = blk(block, i);
        z += (w ^ x ^ y) + block[i] + 0x6ed9eba1 + rol(v, 5);
        w = rol(w, 30);
    }

    inline void
    R3(std::uint32_t block[BLOCK_INTS],
       std::uint32_t v,
       std::uint32_t& w,
       std::uint32_t x,
       std::uint32_t y,
       std::uint32_t& z,
       std::size_t i) {
        block[i] = blk(block, i);
        z += (((w | x) & y) | (w & x)) + block[i] + 0x8f1bbcdc + rol(v, 5);
        w = rol(w, 30);
    }

    inline void
    R4(std::uint32_t block[BLOCK_INTS],
       std::uint32_t v,
       std::uint32_t& w,
       std::uint32_t x,
       std::uint32_t y,
       std::uint32_t& z,
       std::size_t i) {
        block[i] = blk(block, i);
        z += (w ^ x ^ y) + block[i] + 0xca62c1d6 + rol(v, 5);
        w = rol(w, 30);
    }

    inline void make_block(std::uint8_t const* p, std::uint32_t block[BLOCK_INTS]) {
        for (std::size_t i = 0; i < BLOCK_INTS; i++)
            block[i] = (static_cast<std::uint32_t>(p[4 * i + 3]))
                | (static_cast<std::uint32_t>(p[4 * i + 2])) << 8
                | (static_cast<std::uint32_t>(p[4 * i + 1])) << 16
                | (static_cast<std::uint32_t>(p[4 * i + 0])) << 24;
    }

    template<class = void>
    void transform(std::uint32_t digest[], std::uint32_t block[BLOCK_INTS]) {
        std::uint32_t a = digest[0];
        std::uint32_t b = digest[1];
        std::uint32_t c = digest[2];
        std::uint32_t d = digest[3];
        std::uint32_t e = digest[4];

        R0(block, a, b, c, d, e, 0);
        R0(block, e, a, b, c, d, 1);
        R0(block, d, e, a, b, c, 2);
        R0(block, c, d, e, a, b, 3);
        R0(block, b, c, d, e, a, 4);
        R0(block, a, b, c, d, e, 5);
        R0(block, e, a, b, c, d, 6);
        R0(block, d, e, a, b, c, 7);
        R0(block, c, d, e, a, b, 8);
        R0(block, b, c, d, e, a, 9);
        R0(block, a, b, c, d, e, 10);
        R0(block, e, a, b, c, d, 11);
        R0(block, d, e, a, b, c, 12);
        R0(block, c, d, e, a, b, 13);
        R0(block, b, c, d, e, a, 14);
        R0(block, a, b, c, d, e, 15);
        R1(block, e, a, b, c, d, 0);
        R1(block, d, e, a, b, c, 1);
        R1(block, c, d, e, a, b, 2);
        R1(block, b, c, d, e, a, 3);
        R2(block, a, b, c, d, e, 4);
        R2(block, e, a, b, c, d, 5);
        R2(block, d, e, a, b, c, 6);
        R2(block, c, d, e, a, b, 7);
        R2(block, b, c, d, e, a, 8);
        R2(block, a, b, c, d, e, 9);
        R2(block, e, a, b, c, d, 10);
        R2(block, d, e, a, b, c, 11);
        R2(block, c, d, e, a, b, 12);
        R2(block, b, c, d, e, a, 13);
        R2(block, a, b, c, d, e, 14);
        R2(block, e, a, b, c, d, 15);
        R2(block, d, e, a, b, c, 0);
        R2(block, c, d, e, a, b, 1);
        R2(block, b, c, d, e, a, 2);
        R2(block, a, b, c, d, e, 3);
        R2(block, e, a, b, c, d, 4);
        R2(block, d, e, a, b, c, 5);
        R2(block, c, d, e, a, b, 6);
        R2(block, b, c, d, e, a, 7);
        R3(block, a, b, c, d, e, 8);
        R3(block, e, a, b, c, d, 9);
        R3(block, d, e, a, b, c, 10);
        R3(block, c, d, e, a, b, 11);
        R3(block, b, c, d, e, a, 12);
        R3(block, a, b, c, d, e, 13);
        R3(block, e, a, b, c, d, 14);
        R3(block, d, e, a, b, c, 15);
        R3(block, c, d, e, a, b, 0);
        R3(block, b, c, d, e, a, 1);
        R3(block, a, b, c, d, e, 2);
        R3(block, e, a, b, c, d, 3);
        R3(block, d, e, a, b, c, 4);
        R3(block, c, d, e, a, b, 5);
        R3(block, b, c, d, e, a, 6);
        R3(block, a, b, c, d, e, 7);
        R3(block, e, a, b, c, d, 8);
        R3(block, d, e, a, b, c, 9);
        R3(block, c, d, e, a, b, 10);
        R3(block, b, c, d, e, a, 11);
        R4(block, a, b, c, d, e, 12);
        R4(block, e, a, b, c, d, 13);
        R4(block, d, e, a, b, c, 14);
        R4(block, c, d, e, a, b, 15);
        R4(block, b, c, d, e, a, 0);
        R4(block, a, b, c, d, e, 1);
        R4(block, e, a, b, c, d, 2);
        R4(block, d, e, a, b, c, 3);
        R4(block, c, d, e, a, b, 4);
        R4(block, b, c, d, e, a, 5);
        R4(block, a, b, c, d, e, 6);
        R4(block, e, a, b, c, d, 7);
        R4(block, d, e, a, b, c, 8);
        R4(block, c, d, e, a, b, 9);
        R4(block, b, c, d, e, a, 10);
        R4(block, a, b, c, d, e, 11);
        R4(block, e, a, b, c, d, 12);
        R4(block, d, e, a, b, c, 13);
        R4(block, c, d, e, a, b, 14);
        R4(block, b, c, d, e, a, 15);

        digest[0] += a;
        digest[1] += b;
        digest[2] += c;
        digest[3] += d;
        digest[4] += e;
    }

    struct sha1_context {
        static unsigned int constexpr block_size = sha1::BLOCK_BYTES;
        static unsigned int constexpr digest_size = 20;

        std::size_t buflen;
        std::size_t blocks;
        std::uint32_t digest[5];
        std::uint8_t buf[block_size];
    };

    template<class = void>
    void init(sha1_context& ctx) noexcept {
        ctx.buflen = 0;
        ctx.blocks = 0;
        ctx.digest[0] = 0x67452301;
        ctx.digest[1] = 0xefcdab89;
        ctx.digest[2] = 0x98badcfe;
        ctx.digest[3] = 0x10325476;
        ctx.digest[4] = 0xc3d2e1f0;
    }

    template<class = void>
    void update(sha1_context& ctx, void const* message, std::size_t size) noexcept {
        auto p = reinterpret_cast<std::uint8_t const*>(message);
        for (;;) {
            auto const n = (std::min)(size, sizeof(ctx.buf) - ctx.buflen);
            std::memcpy(ctx.buf + ctx.buflen, p, n);
            ctx.buflen += n;
            if (ctx.buflen != 64)
                return;
            p += n;
            size -= n;
            ctx.buflen = 0;
            std::uint32_t block[sha1::BLOCK_INTS];
            sha1::make_block(ctx.buf, block);
            sha1::transform(ctx.digest, block);
            ++ctx.blocks;
        }
    }

    template<class = void>
    void finish(sha1_context& ctx, void* digest) noexcept {
        using sha1::BLOCK_BYTES;
        using sha1::BLOCK_INTS;

        std::uint64_t total_bits = (ctx.blocks * 64 + ctx.buflen) * 8;
        // pad
        ctx.buf[ctx.buflen++] = 0x80;
        auto const buflen = ctx.buflen;
        while (ctx.buflen < 64)
            ctx.buf[ctx.buflen++] = 0x00;
        std::uint32_t block[BLOCK_INTS];
        sha1::make_block(ctx.buf, block);
        if (buflen > BLOCK_BYTES - 8) {
            sha1::transform(ctx.digest, block);
            for (size_t i = 0; i < BLOCK_INTS - 2; i++)
                block[i] = 0;
        }

        /* Append total_bits, split this uint64_t into two uint32_t */
        block[BLOCK_INTS - 1] = total_bits & 0xffffffff;
        block[BLOCK_INTS - 2] = (total_bits >> 32);
        sha1::transform(ctx.digest, block);
        for (std::size_t i = 0; i < sha1::DIGEST_BYTES / 4; i++) {
            std::uint8_t* d = reinterpret_cast<std::uint8_t*>(digest) + 4 * i;
            d[3] = ctx.digest[i] & 0xff;
            d[2] = (ctx.digest[i] >> 8) & 0xff;
            d[1] = (ctx.digest[i] >> 16) & 0xff;
            d[0] = (ctx.digest[i] >> 24) & 0xff;
        }
    }
} // namespace sha1
} // namespace moon

#endif
